Below are steps on how to create a content compliance rule.
1. Sign in to Admin panel
2. Google Apps > Gmail
3. Scroll down to Content compliance> Click on configure.
4. In select inbound, outbound, internal-sending and internal receiving.
5. On section 2. Add expressions that describe the content you want to search for in each message - click on add then select advance content match
6.On option 3 select the option "Reject Message" then add a custom rejection message.
7.On option 4 deselect the bypass this setting option then save the above changes.